Since the invention of integrated circuits, the semiconductor industry has experienced continuous rapid growth due to constant improvements in the integration density of various electronic components (i.e., transistors, diodes, resistors, capacitors, etc.) and semiconductor packages. For the most part, these improvements in integration density have come from repeated reductions in minimum feature size, allowing more components to be integrated into a semiconductor chip or package.
One approach for allowing more components to be integrated into a semiconductor package is the adoption of flip chip structures, in which a semiconductor chip is bonded to a substrate with conductive bumps and also the semiconductor chip is “flipped” onto the active circuit surface. Such flip chip package has a problem that it is subject to different temperatures during the packaging process. As a result, the package is highly stressed due to the different coefficients of thermal expansion (CTE) of the various package substrate and chip materials, which in turn may cause the substrate to bow, warp or crack. Accordingly, what is needed are package structures that can control package warpage (e.g., co-planarity) within acceptable limits and that absorb the package's internal stresses to enhance the reliability.